It was the perfect place to grow marijuana: a section of the rhinoceros pen that only one zookeeper had access to. A zookeeper in Austria thought he would never be caught.

Salzburg Hellbrunn Zoo director Sabine Grebner said today (Mon): "It’s horrible! We never thought such a thing was possible. We are here for families and kids – and we don’t have anything to do with drugs."

Police said the 59-year-old rhinoceros carer kept 33 marijuana plants in a part of the enclosure which is hidden from visitors’ view, adding that they acted on an anonymous tip-off by "customer" of the offender.